The utility of RF electrosurgical snares for detaching tissue structures and creating/maintaining hemostasis in both open and endoscopic surgery has been identified and addressed previously by a number of designs. U.S. Pat. Nos. 3,805,791, 3,910,279, 3,955,578, 4,202,338, and 4,345,599 describe snares that employ monopolar RF energy to cut and coagulate tissue. Although highly efficient cutting devices, the monopolar technology upon which these designs are based requires relatively high power levels and is generally associated with greater amounts of collateral tissue damage and increased risk of patient injury resulting from the inadvertent flow of current.
U.S. Pat. Nos. 3,901,242, 4,311,143, 4,493,320, 4,905,691, 5,078,716, 5,318,564, and 6,050,995 describe improved versions of the previously referenced monopolar designs which utilize bipolar RF energy to accomplish cutting. Use of bipolar instrumentation is generally associated with lower power levels, reduced amounts of collateral tissue damage and enhanced patient safety. However, conventional bipolar technology does not readily generate the current densities required for effective and rapid tissue cutting.
These known snare instruments typically consist of an insulated handle/introducer which is used to introduce the snare into the surgical site and manipulate it during use, and a section of exposed wire which can be deployed from the introducer to form a loop or lasso that captures therein the tissue to be resected. The snare instrument is introduced into the body, such as through an endoscope, with the snare in the retracted position within an introducer. When the distal end of the instrument is in close proximity to the target tissue, the snare is then fully deployed out of the end of the introducer. A grasper or other suitable device is used to grasp the end of the snare, loop it around the target tissue, and then insert it into a suitable capture mechanism on the instrument to cause the snare to form the loop referred to above. The energy source, such as a generator, is then activated while the snare is pulled toward the proximal side of the tissue to cut and cauterize the target tissue. These devices suffer from the drawbacks mentioned above.
U.S. Pat. Nos. 5,697,281, 5,697,536, 5,697,882, and 5,697,909 describe bipolar electrosurgery technology that uses a plasma pocket or bubble to provide rapid tissue vaporization or cutting with reduced collateral tissue damage as compared to monopolar electrosurgery. These patents describe a custom generator which is capable of forming and maintaining this plasma bubble in a conductive fluid media, such as normal saline, and a collection of electrodes which can be used to cut and vaporize/remove tissue. None of these prior art references or devices they disclose, however, teach or suggest the incorporation of plasma technology into an electrosurgical snare in order to overcome the deficiencies of presently existing snares as described above.
Accordingly, there is a need for an improved electrosurgical snare based on plasma technology that provides the rapid and efficient cutting commonly found only with monopolar instruments while also providing the increased safety associated with bipolar electrosurgery.